Physical exercise often involves modifying a multi-phase biorhythmic activity, such as breathing. Breathing patterns display irregularities in a number of cardiovascular diseases, including congestive heart failure (CHF), and pulmonary diseases, including chronic obstructive pulmonary disease (COPD). These irregularities are known markers for disease-related mortality and morbidity. Typical irregularities include Cheyne-Stokes breathing (recurrent episodes of central apnea alternating with hyperpnea), amplitude-modulated breathing (periodic breathing) at a rate of about one modulation per minute, repeated sighs, and breathing at random amplitudes and periods. A reduction in breathing pattern irregularity indicates an improvement in health. The impairment of cardiovascular reflexes, which control blood pressure and volume in an attempt to minimize fluctuations in blood supply to organs, is also clinically significant in cardiovascular and psychosomatic diseases.
U.S. Pat. Nos. 5,076,281, 5,800,337, and 6,090,037 to Gavish, which are incorporated herein by reference, describe methods and devices for modifying biorhythmic activity by measuring one or more variables of a user. The patents describe the generation of a stimulus, which is provided to the user, so as to change the biorhythmic activity of a user in a way that relates in a predetermined way to the monitored biorhythmic activity. The '037 additionally describes a respiration sensor.
U.S. Pat. No. 5,423,328 to Gavish, which is incorporated herein by reference, describes a stress-detecting device for monitoring respiration, and, in particular, a method for detecting and monitoring circumferential changes in the chest or abdomen of a user resulting from breathing.
U.S. Pat. No. 6,662,032 to Gavish et al., which is incorporated herein by reference, describes techniques for facilitating improving health of a user, including a first sensor, adapted to measure a first physiological variable, which is indicative of a voluntary action of the user; a second sensor, adapted to measure a second physiological variable, which is not entirely under the direct voluntary control of the user; and circuitry, adapted to receive respective first and second sensor signals from the first and second sensors, and responsive thereto, to generate an output signal which directs the user to modify a parameter of the voluntary action.
US Patent Application Publication 2004/0116784 to Gavish, which is incorporated herein by reference, describes apparatus including a sensor, adapted to generate a sensor signal indicative of biorhythmic activity of a user of the apparatus, the sensor signal having a first characteristic, indicative of a voluntary action of the user, and a second characteristic, indicative of a benefit-related variable of the user.
PCT Publication WO 04/014226 to Gavish, which is incorporated herein by reference, describes apparatus including a memory for storing a set of computer instructions, the memory adapted to have stored therein an initial form of a multi-phase biorhythmic activity pattern and an indication of a desired form of the multi-phase biorhythmic activity pattern, wherein a ratio of durations of two phases in the desired form is different from a ratio of durations of the respective phases in the initial form, and wherein at least one phase of the multi-phase biorhythmic activity pattern corresponds to a respective phase of a multi-phase biorhythmic activity of the subject.
Intercure, Inc. (Fort Lee, N.J., USA and Lod, Israel) markets RESPeRATE™, a device that utilizes some of the techniques described in the above-referenced patents and patent application publications. This device for modifying biorhythmic activity includes an input for the respiration signal, a central processing unit, memory, a sound synthesizing chip, and output to earphones.
U.S. Pat. No. 5,734,090 to Koppel et al., which is incorporated herein by reference, describes a method and apparatus for verifying an expiratory breath flow (e.g., for determining a degree of alcohol in the breath), utilizing the sonic characteristics of a standardized breath as a reference.
U.S. Pat. No. 6,726,636 to Der Ghazarian et al., which is incorporated herein by reference, describes a voice recognition breathalyzer comprising a microphone for transducing spoken expression into electronic signals and a breathalyzer sensor for transducing a given breath content into electronic signals.
U.S. Pat. No. 5,509,414 to Hok, which is incorporated herein by reference, describes techniques for detecting air flow at the mouth and nose of a subject, including a transducer for converting electrical signals into ultrasound waves and vice versa, means for directing the ultrasound waves toward the mouth and nose of the subject and receiving return waves, and a detector to analyze electrical signals converted by the transducer from the return ultrasound waves.
U.S. Pat. No. 5,195,528 to Hok, which is incorporated herein by reference, describes an acoustic respiration detector including at least two tubular air transmission lines having ends which are connected to microphone elements. Close to the other ends of the lines are openings at which turbulence, and hence acoustic signals, are created by the incidence of airflow caused by respiration. A holding element secures the openings relative to the mouth or nose of a patient whose respiratory function is to be monitored, and a flow-directing element, for example formed like a face mask, directs the airflow to the openings. The microphone elements are connected in a bridge circuit with two voltage supplying leads and at least one signal lead. This arrangement is described as suppressing sensitivity to mechanical and acoustic disturbances.
U.S. Pat. No. 5,797,852 to Karakasoglu et al., which is incorporated herein by reference, describes sleep apnea screening and/or detection apparatus for use by a patient breathing through the nose and/or mouth and producing an air flow into and out of the lungs of the patient and creating audible sounds.
U.S. Pat. No. 6,150,941 to Geiger et al., which is incorporated herein by reference, describes a stand-off, non-invasive acoustic detector for monitoring physical activity and/or breathing activity of children and infants.
U.S. Pat. No. 6,261,238 to Gavriely, which is incorporated herein by reference, describes a method for analyzing breath sounds produced by a respiratory system, the method comprising: measuring breath sounds produced by the respiratory system; tentatively identifying a signal as being caused by a breath sound of a given type if it meets a first criteria characteristic of the breath sound of the given type; and confirming said identification if a tentatively identified signal meets a second criteria characteristic of the breath sound of the given type.
The following patents, all of which are incorporated herein by reference, may be of interest:    U.S. Pat. No. 4,195,626 to Schweizer    U.S. Pat. No. 5,678,571 to Brown    U.S. Pat. No. 5,596,994 to Bro    U.S. Pat. No. 4,883,067 to Knispel et al.    U.S. Pat. No. 4,798,538 to Yagi    U.S. Pat. No. 5,827,179 to Lichter et al.    U.S. Pat. No. 6,001,065 to DeVito    U.S. Pat. No. 5,921,890 to Miley    U.S. Pat. No. 5,027,686 to Ishikawa    U.S. Pat. No. 6,212,135 to Schreiber    U.S. Pat. No. 4,711,585 to Fresquez et al.
The following articles, all of which are incorporated herein by reference, may be of interest:    Cooke et al., “Controlled breathing protocols probe human autonomic cardiovascular rhythms,” American Journal of Physiology 274:H709-H718 (1998)    Pitzalis et al., “Effect of respiratory rate on the relationship between RR interval and systolic blood pressure fluctuations: a frequency-dependent phenomenon,” Cardiovascular Research 38:332-339 (1998)    Bernardi et al., “Effect of breathing rate on oxygen saturation and exercise performance in chronic heart failure,” The Lancet 351:1308-1311 (1998)    Mortara et al., “Abnormal awake respiratory patterns are common in chronic heart failure and may prevent evaluation of autonomic tone by measures of heart rate variability,” Circulation 96:246-252 (1997)    La Rovere et al., “Baroreflex sensitivity and heart-rate variability in prediction of total cardiac mortality after myocardial infarction,” The Lancet 351:478-484 (1998)